Although several species of small, oily fish may properly be called herrings, by far the most abundant available in the UK is the Atlantic herring, a fish that has been an essential and sustaining food source for many thousands of years. For some communities and countries it was or is essential to the national economy.
The herring’s particular advantage is that the diverse species each breed in a different season, meaning there are usually fish to harvest, whatever nature has done to other land or sea crops.
Their oiliness means that as well as being nourishing and gratifying to eat fresh, herrings can be pickled, salted and/or smoked and thus stored as a reliable food source throughout the year.
Choose the best
Herrings are available in so many guises that it's impossible to give guidance that's relevant to all. But if you're buying them fresh, the advice is the same as for all fresh fish. They should not smell fishy, the eyes should be bright and the gills must be red rather than brown; generally it's safer to buy them frozen and defrost them slowly if you're not certain about those offered fresh.
Fresh herrings have a very short life and should be cooked and eaten very quickly.
Smoked herrings come as bloaters, buckling or kippers and last least long in that order; bloaters and buckling must be supple and not curled or dry-skinned and traditionally were eaten on the day of manufacture or very, very soon afterwards. See kippers for more advice.
Pickled/salted herring fillets, sold as rollmops (usually stuffed and eaten just as they are), matjesfillets and other types last a long time because of the preservative qualities of the brine/vinegar solutions in which they're stored. Unless kept submerged, the raw onion used in some versions will oxidise and give most unpleasant flavours although even these have their friends. Salted herrings are not stored in a liquid and benefit from being soaked in water or milk before being used.
Other than the smoked varieties, salted and preserved herrings all have friends and implacable enemies. The most challenging style of all is called surstromming. These are Baltic herrings matured in barrels with only half the usual amount of salt. They are eaten only after the barrels bulge and are then broached in the open air with a cut onion held to your nose; there are tales of birds dropping dead from the air.
Fresh herrings are especially good grilled or fried, often with a coating of oatmeal, which absorbs some of the oil that would otherwise be lost and which is so good for us.